Sheet-size detecting mechanism

ABSTRACT

A sheet-size detecting mechanism includes a sheet holder composed of a paper tray and a paper guide. The mechanism also includes a logic board and a sensor module. Adjusting the width of the paper guide corresponding to the sheet width may cause a lot of digital information to be generated due to relative motion between the logic board and the sensor module. Then the sheet-size may be determined accordingly.

FIELD OF THE INVENTION

[0001] The present invention relates to a detecting mechanism used on an image scanning device so as to automatically detect the size of the sheet of a document to be scanned.

BACKGROUND OF THE INVENTION

[0002] A conventional scanner has to be connected to a computer and a preview procedure is taken before scanning the sheet of document and a proper or preferable size or range is chosen to be scanned. Alternatively, the image of the document that is scanned by the scanner is sent to the software for dealing with the images, and then the user chooses the desired range. Therefore, the conventional scanner needs not to detect the size of the sheet frequently.

[0003] An automatic document feeder is usually cooperated with the scanner and generally is an A4-size automatic document feeder because this size of sheet is often used so that the conventional scanners do not equip with the sheet-size detecting mechanism.

[0004] If an A3-size automatic document feeder is used, the A4 sheets can also be fed in transverse direction so as to reduce the period of time of scanning. This benefit is especially significant when a lot amount of sheets are to be scanned. Nevertheless, the sheet-size detecting mechanism has to be able to distinguish the sheet size such as the A3 sheets and A4 sheets. Therefore, the sheet-size detecting mechanism is necessary.

[0005] Besides, the peripheral devices of computers are gradually combined as a multi-function machines, or the digital copy machines and scanners are connected with each other. Before using the multi-function machines or the copy machines, the sheet size has to be decided and then scanning the sheets while printing. This may obtain a better efficiency so that a sheet-size detecting mechanism for detecting the sizes of sheets is necessary.

[0006] A mechanical-electrical sheet-size detecting device is a detecting switch which could malfunction if the sheet is too thin. Besides, one part can only detect one size of the sheets and the same amount of parts is needed when detecting the amount sheets of paper. The parts occupy too much space and the number of the sheets is limited, therefore, the number of sizes of the sheets is limited.

[0007] Another resistor type sheet-size detecting mechanism includes a sheet guiding plate which has a conductive member thereon which is moved relative to the resistor on the circuit board. The resistance difference generated from the position difference between the conductive member and the resistor results in a difference of electric current or voltage which corresponds to the different sizes of sheets. However, the frequent movement and friction between the conductive member and the resistor reduces the term of use of the sheet-size detecting mechanism. Besides, the fluctuation of the current or the electric voltage and the complicity of the sheet sizes result malfunctions in detection of the sheet sizes. It does not meet the requirements if the detecting mechanism can only detect few sizes of the sheets.

[0008] Electric capacitor type and inductor type sheet-size detecting mechanisms employ the same feature to detect the sizes of the sheets and the functions are similar to those obtained by the resistor type sheet-size detecting mechanism.

SUMMARY OF THE INVENTION

[0009] The first object of the present invention is to provide a sheet-size detecting mechanism which is used to detect the size of the sheet in the automatic document feeder.

[0010] The second object of the present invention is to provide a sheet-size detecting mechanism which employs the relative movement between a logic board and a sensor module so as to detect the width of the sheet.

[0011] The third object of the present invention is to provide a sheet-size detecting mechanism which may detect the width of the sheet by way of the logic arrangements.

[0012] The fourth object of the present invention is to provide a sheet-size detecting mechanism which has a sensor module put in the lengthwise direction of the sheets so as to recognize the different lengths of the sheets with the same width.

[0013] The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a perspective view to show the combination of the scanner and the mechanism of the present invention.

[0015]FIG. 2 is a perspective view to show the mechanism of the present invention.

[0016]FIG. 3 is an enlarged view to show a part of the mechanism of the present invention.

[0017]FIG. 4 shows the logic board and the sensor modules.

[0018]FIG. 5A shows the first position of the sheet-size detecting mechanism.

[0019]FIG. 5B shows the second position of the sheet-size detecting mechanism.

[0020]FIG. 5C shows the third position of the sheet-size detecting mechanism.

[0021]FIG. 5D shows the fourth position of the sheet-size detecting mechanism.

[0022]FIG. 5E shows the fifth position of the sheet-size detecting mechanism.

[0023]FIG. 5F shows the sixth position of the sheet-size detecting mechanism.

[0024]FIG. 5G shows the seventh position of the sheet-size detecting mechanism.

[0025]FIG. 5H shows the eighth position of the sheet-size detecting mechanism.

[0026]FIG. 6 is a chart to show the signals that the sensor module outputs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] Referring to FIG. 1, an automatic document feeder module comprises an input tray 10 and an output tray 20. The input tray 10 receives the document to be scanned. The sheets of the document can be automatically fed in by an automatic document feeder.

[0028] Referring to FIG. 2, the input tray 10 includes a plate 12 and two paper guides 14, 16. The surface of the plate 12 is defined as a facing surface 13 on which sheets are put and the opposite surface of the plate 12 is defined as a bottom 15.

[0029] The two paper guides 14, 16 are located on the plate 12 and protrude from the facing surface 13. The two paper guides 14, 16 can be moved toward or away from each other.

[0030] Referring to FIGS. 3 and 4, a sensor module 30 is fixed to the bottom 15 of the plate 12 and has a plurality of sensors 32A, 32B, 34A, 34B, 36A and 36B.

[0031] The sensors 32A and 32B are together to be a sensing unit 32, the sensors 34A and 34B are together to be a sensing unit 34, and the sensors 36A and 36B are together to be a sensing unit 36.

[0032] A passage 33 is defined between the sensors 32A, 32B, a passage 35 is defined between the sensors 34A, 34B, and a passage 37 is defined between the sensors 36A, 36B.

[0033] A logic board 40 is mounted to the bottom 15 of the plate 12 and is fixed to the paper guide 14 such that the logic board 40 is able to move with the paper guide 14. The logic board 40 has ribs 42 extending from the surface and the ribs 42 are located corresponding to the passages 33, 35, 37. Gaps 44 are defined between the ribs 42 in the same row. The logic board 40 moves with the movement of the paper guide 14 such that the ribs 42 may enter or leave the passages 33, 35, 37.

[0034]FIG. 4 shows that none of the ribs 42 enters the passages 33, 35, 37 of the sensor module 30. Therefore, the sensing units 32, 34 and 36 are not separated and they are in an open status which is defined as a digit “1”. On the contrary, the sensing units 32, 34 and 36 may be separated and in a close status which is defined as a digit “0”.

[0035] Referring to FIGS. 5A and 6, when the ribs 42 and the sensing units 32, 34 and 36 are located in the status as shown in FIG. 5A, because the sensing units 32, 34 and 36 are not located in correspondence with the ribs 42, the sensing units 32, 34 and 36 are in the open status. A result is obtained as shown in FIG. 6A and the status is defined as a digit information “111”.

[0036] Referring to FIGS. 5B and 6, when the ribs 42 and the sensing units 32, 34 and 36 are located in the status as shown in FIG. 5B, because the sensing unit 32 is separated, sensing units 34 and 36 are not located in correspondence with the ribs 42 to form an open status. A result is obtained as shown in FIG. 6B and the status is defined as a digit information “011”.

[0037] Referring to FIGS. 5C and 6, when the ribs 42 and the sensing units 32, 34 and 36 are located in the status as shown in FIG. 5C, because the sensing units 32 and 34 are separated, the sensing unit 36 is not located in correspondence with the ribs 42 to form an open status. A result is obtained as shown in FIG. 6C and the status is defined as a digit information “001”.

[0038] Referring to FIGS. 5D and 6, when the ribs 42 and the sensing units 32, 34 and 36 are located in the status as shown in FIG. 5D, because all the sensing units 32, 34 and 36 are located in correspondence with the ribs 42 so that the sensing units 32, 34, 36 are in close statuses. A result is obtained as shown in FIG. 6D and the status is defined as a digit information “000”.

[0039] Referring to FIGS. 5E and 6, when the ribs 42 and the sensing units 32, 34 and 36 are located in the status as shown in FIG. 5E, because the sensing unit 32 is not located in correspondence with the ribs 42 and the sensing units 34 and 36 are separated by the ribs 42 to form a close status. A result is obtained as shown in FIG. 6E and the status is defined as a digit information “100”.

[0040] Referring to FIGS. 5F and 6, when the ribs 42 and the sensing units 32, 34 and 36 are located in the status as shown in FIG. 5F, because the sensing units 32 and 34 are not located in correspondence with the ribs 42 and the sensing unit 36 is separated by the rib 42 to form a close status. A result is obtained as shown in FIG. 6F and the status is defined as a digit information “110”.

[0041] Referring to FIGS. 5G and 6, when the ribs 42 and the sensing units 32, 34 and 36 are located in the status as shown in FIG. 5G, because the sensing units 32 and 36 are separated by the ribs 42 and the sensing unit 34 is not located in correspondence with the rib 42 to form an open status. A result is obtained as shown in FIG. 6G and the status is defined as a digit information “010”.

[0042] Referring to FIGS. 5H and 6, when the ribs 42 and the sensing units 32, 34 and 36 are located in the status as shown in FIG. 5H, because the sensing units 32 and 36 are not located in correspondence with the rib 42 and the sensing unit 34 is separated by the rib 42 to form a close status. A result is obtained as shown in FIG. 6H and the status is defined as a digit information “101”.

[0043] By the movement of the logic board 40 relative to the sensing units 32, 34, 36, there are eight arrangements obtained. By adjusting the position of the paper guide 14, the width of the sheets on the plate 12 can be detected and eight different widths can be detected. It is understandable that the number of the widths of the sheets that can be detected by the sheet-size detecting mechanism increases in a way of powers of a base which is 2, by increasing the number of the sensor modules 30 and the number of the ribs 42 on the logic board 40.

[0044] By using the relative movement of the logic board 40 and the sensor modules 30, the ribs 40 on the logic board 40 can be moved corresponding to the sensing units 32, 34, 36 of the sensor module 30 so as to form several results and decide the width of the sheets accordingly. In the above mentioned embodiment, the logic board 40 is movable and the sensor module 30 is fixed. It is also available that the logic board 40 is fixed and the sensor module 30 is movable.

[0045] Referring to FIG. 2, the plate 12 has a sensor 18 which is located in parallel with the direction that the sheets move, preferably located away from the input end 19. The purpose of the installation of the sensor 18 is to detect the longitudinal direction of the sheet. Because the sheet is rectangular so that there is a difference for the sheet to be fed in a specific direction, such as the A3 sheets and the transverse A4 sheets have the same width, so that the length of the sheet can be recognized by using the sensor 18.

[0046] The comparison between the sensor module 30 and the logic board 40 is cooperated with the result from the sensor 18 so as to obtain 8×2=16 different results.

[0047] In the above mentioned embodiment, the sensors output a signal according to the separation by the ribs so that the sensors are penetration sensors. However, reflection sensors can be used to replace the penetration sensors. The reflection sensors submit signals and detect the responses whether or not the signals bounce back by the ribs so as to have different information. Holes or recesses are defined in the logic board when using the reflection sensors. It is to be noted that the recesses, holes and the ribs are called feature sections on the logic board.

[0048] Therefore, the present invention uses logic arrangements so as to reduce the number of the sensors and can detect more types of sheet sizes. This reduces the manufacturing cost and can precisely detect the sizes of the sheets. The sensors for detecting the sizes of the sheets do not need to contact the sheets so that they are not worn out and may keep the precision.

[0049] While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention. 

What is claimed is:
 1. A sheet-size detecting mechanism comprising: a plate having a facing surface and a bottom which is located in opposite to the facing surface; a logic board having a plurality of feature sections on a surface thereof and the logic board being located at the bottom of the plate; a sensor module located at the bottom of the plate, and at least one paper guide movably mounted to the plate, the logic board being movable relative to the sensor module, the sensor module generating signals by relative movements between the feature sections and the sensor module.
 2. The mechanism as claimed in claim 1, wherein the logic board is connected to the paper guide.
 3. The mechanism as claimed in claim 1, wherein the sensor module is connected to the paper guide.
 4. The mechanism as claimed in claim 1, wherein the feature sections on the logic board are plurality of ribs and gaps are defined between the ribs.
 5. The mechanism as claimed in claim 1 further comprising sensors on the facing surface of the plate.
 6. The mechanism as claimed in claim 1, wherein the sensor module is composed of plurality of sensing units.
 7. The mechanism as claimed in claim 6, wherein each sensing unit is composed of two sensors between which a passage is defined.
 8. The mechanism as claimed in claim 1, wherein the feature sections of the logic board are recesses.
 9. The mechanism as claimed in claim 1, wherein the feature sections of the logic board are holes. 